Solar Panels UK - is it worth it?

[ACarneiro]

As many panels as you can fit/afford, I’d say.
Battery storage is trickier as it’s unlikely to have a ROI (electricity prices won’t stay this high for very long), so it kinda boils down to how much you value energy security and the “smug factor”

 

[Avendit]

I am thinking to pull the trigger on Solar installation. I will get some estimators coming later this week

my roof is east / west.
we both work from home most of the days (wife is always WFH) and she loves to run washing machine/dryer (sometimes both at the same time) during the day

what you guys think is the best capacity, including battery, to install??

10 panels east + 10 panels west?

Biggest you can install and finance. More is simply more. The bigger you go, the more you save more of the year. A big part of the cost is scaffold and paying people to organise and turn up. Each panel is only £140ish - incremental cost to upsizing is tiny, adding later will re-incur all those base costs.

At least that was my logic. Some parts shortages limited me by 3 panels on my SW array, and I limited the NE facing array for asthetic reasons and a bit of a mental block about having more panels facing N than S.

8 NE, 11 SW, pulling in 20-35kw a day since I stall 3 weeks ago

 

[yessuz]

As many panels as you can fit/afford, I’d say.
Battery storage is trickier as it’s unlikely to have a ROI (electricity prices won’t stay this high for very long), so it kinda boils down to how much you value energy security and the “smug factor”

not much, really.

I checked and my power bills now are at ~80, depending on charges a month. It will be ~1k a year. so 10 k installation is >10 years pay off.

I just wonder if battery is really worth it.

 

[scdoubleu]

I'll second the "as many as you can fit" statement, on both roof aspects. Subject to DNO limitations.

We have 9 x 385w panels facing SSE on a detached double garage and 10 x 385w facing WSW on the house. I wanted 16 on the WSW house roof, and an additional 6 on the ENE facing house roof but the DNO said no.

As it is, both arrays are clipping for a decent chunk of the day this time of year. During the winter, the garage array provides the bulk (which is not a lot) of our solar power. You may find winter to be pretty poor without a south-facing array. This is when having ESS really excels.

When we did the ROI calculations last summer, payback was in excess of 10 years (we have one Powerwall). Looking at SWMBO's spreadsheet, this has dropped to around 8 years at current rates.

 

[Avendit]

not much, really.

I checked and my power bills now are at ~80, depending on charges a month. It will be ~1k a year. so 10 k installation is >10 years pay off.

I just wonder if battery is really worth it.

Add in the ability to use cheap rate power to fill the battery in the winter and the payoff is around the same as time as panels. For me that is currently about 6 years, will be less if power costs go up as predicted in the next 6 months. But it depends on your usage (ie I'm on electric heat pump for all heating needs). Time to break out excel I'm afraid!

 

[Avendit]

Add in the ability to use cheap rate power to fill the battery in the winter and the payoff is around the same as time as panels. For me that is currently about 6 years, will be less if power costs go up as predicted in the next 6 months. But it depends on your usage (ie I'm on electric heat pump for all heating needs). Time to break out excel I'm afraid!

Also, to be fair I've not calculated how they interact with gas heating at all if you are still using that...

 

[Mrklaw]

roughly I seemed to home in on around enough battery storage to get you from ‘end of solar day’ to ‘start of off peak period’. so for me I was working on about 18:30 through to 00:30 which is around 7kwh. That works providing you can end the solar day with a full battery.

In winter or low solar days, a larger battery would help with charging overnight and covering during the day. So the max size would be either
- your entire peak usage
- the amount you can charge overnight given off peak windows and inverter limits. (eg if you can only charge at 3kw for 4 hours octopus go, no point having a battery much bigger than 12kwh as you can’t charge overnight and if you have solar you shouldn’t need that much anyway)


how many kwh do you use per day on average? ballpark your numbers seem about right

 

[Lx2m3]

One option to consider is a Powerwall and as many solar panels you can afford, subject to DNO approval then sign up to the Tesla Energy Plan, currently 12p tariff either input or export (my area), no time scheduling for usage necessary.

 

[WannabeOwner]

my roof is east / west

I think that is better than just South

I have East and South, and it is apparent that if I had some West PV that would give me an hour or so more at the end of the day before the Battery has to take the load ... and thus Battery would more easily get me to "Solar Up" the following day

I really appreciate the early-start of East - I'm generating usefully by 06:00, whereas my South is nearer 08:00

My East drops below useful by 19:00, my South by 20:00

I'm finding SOLCAST useful to predict generation. It will only show last 3 previous days "estimate of actuals" and next 3 days prediction, but if there has been a full sun day in that period it might help with some figures (there are other "Generation per year for LATITUDE" type sites, so this may not be your cup-of-tea)

Only lets you set up 2 arrays (in the free version), but whilst fiddling you could change the CONFIGs to try different East / South / West settings and see what it thinks for the past / next 3 days

Solcast - Solar Forecasting & Solar Irradiance Data

enough battery storage to get you from ‘end of solar day’ to ‘start of off peak period’.

I have two levels. 50%-ish will get me from sun-down to start of off-peak, and 99%-ish will get me to sun-up.

But I don't have anything like enough battery for winter to fill during Off Peak than then to last from end-Off-Peak to next Start-Off-Peak

what you guys think is the best capacity

As others have said whilst the scaffolding is up the incremental cost of more panels is modest. But worth considering if you can actually use all of it most of the time.

On perfect-sun-days I get up to 15kW for a couple of hours in the middle of the day (I have 48 panels) ... the house might only be using 1kW, the PowerWalls might be full, so I would have to charge both EVs flat out @ 7KW ... takes a fair bit of organisation to achieve that!

If you have e.g. Zappi that will just dump any excess into the car, that's a simple plug-and-play solution. However, I think it is not perfect. Car thinks it is parked at home and the "Charge at start of Off Peak" schedule will kick in ... but car also needs to be set to "Charge during the day" in case the Zappi has any overspill power ... so fiddling needed to stop that car charging overnight (but also to be sure that the car does charge on Off Peak when you do want that)

Personally I could do with an APP that would take care of this, but I haven't found one (and I can see myself having to cobble something together)

Input the Miles I want to go in each car in the next day or two
Use the Solar Prediction to decide if "Today" will generate more PV than can fit in the PowerWalls
Get the cars to Start Charging if excess PV available (depending on which car has most miles to do in next few days) ...
... charge the cars overnight on Off Peak if they haven't got enough from PV for "Tomorrow's mileage"

FWIW in June I put 400 kWh into the Cars, of which 14.5 kWh was on Off Peak

In terms of ROI my view is:

If you are old enough that likely to be in your current house into retirement then installing PV / Battery is basically locking in the price of X% of your annual electricity (at today's PV / Battery prices). So you won't have to pay that X% to Utility Company in future.

No idea if Electricity price will go up or down - down seems unlikely to me, but anything could happen - but either way I'm more than happy that I no longer pay some 80% of my electricity bill

 

[Zakalwe]

That crimp tool out the whole damn network, just plugging it into the powered down network .


The Andersen has an Advanced Solar option in beta that I'm going to investigate. Otherwise I'll take back manual control and just choose to charge at a limited rate for a few hours. But that sucks.

This is a late reply, but it might help. I installed a CT onto my Andersen to use up excess solar. It works pretty well, but it can be a bit slow to react on days where there is partial cloud cover (the inverter is probably as much to blame here). That means that (assuming you have a home battery) you will find occasions where it drags some power off the battery to meet the car charging demands. There is a way to force it to add grid power when the solar drops, but that defeats the purpose.
The other issue that I have found is that there doesnt seem to be a way to combine Scheduled charge periods with the solar piece. For example, I have my Andersen running on a Schedule to match my Octopus off-peak periods. When I want to use excess solar, I have to cancel the schedule and then change the dial in the app to "Max Solar". This forces the Andersen to only use excess solar to charge.

I have to remember to change it back to "Max Grid" and re-enable the Schedule top charge during the cheap period.

There's probably some clever way of doing this using a script or Home Automation, but that's all witchcraft to a numpty like me!

 

[HenryT]

In terms of ROI my view is:

If you are old enough that likely to be in your current house into retirement then installing PV / Battery is basically locking in the price of X% of your annual electricity (at today's PV / Battery prices). So you won't have to pay that X% to Utility Company in future.

No idea if Electricity price will go up or down - down seems unlikely to me, but anything could happen - but either way I'm more than happy that I no longer pay some 80% of my electricity bill

I have a similar view - some degree of energy independence being the 'gain'.

Already retired and have a modest 8 panel/7.2 kWh battery system which based on experience so far (since Jan,) has provided about 35% of total electricity needs and has significantly reduced (often eliminated) the peak rate consumption.

 

[WannabeOwner]

. I installed a CT onto my Andersen to use up excess solar. It works pretty well, but it can be a bit slow to react on days where there is partial cloud cover (the inverter is probably as much to blame here). That means that (assuming you have a home battery) you will find occasions where it drags some power off the battery to meet the car charging demands. There is a way to force it to add grid power when the solar drops, but that defeats the purpose.

This is where I am at too.

I installed a Zappi assuming I would just "allow any excess to charge the car".

In practice the right car (the one most empty / most needing miles "soon") needs to be attached to the Zappi (other charger is an old Tesla charger), that involves a driveway car-shuffle.

And then the business of overriding overnight schedule and remembering to re-engage it before a trip. Forgetting to enable means having to then stop and supercharge ... forgetting to disable overnight schedule means the car then charges overnight - costs me some money and then the car is full so no capacity to fill up with PV tomorrow ... all 1st world problems of course

I think it would be better if the car said that it wanted to charge, rather than the wall charger controlling that. Wall charger has no idea which car is plugged in / having the greater need for charging (going somewhere soon / lower SOC / Some other criteria)

I'm currently solving this by:

Plug both cars into wall chargers - both enabled to "charge" (rather than being in Eco+ Mode)
Leave the overnight Scheduled charge in place (for when I do want it)
Drop the LIMIT to 50% at the end of the solar-day (unless I want an overnight charge)
(I've set a TeslaFi Schedule @ 16:00 in case I forget; therefore I have to explicitly increase LIMIT on the few occasions when I actually want an overnight charge)
When PV generation is high then increase the LIMIT and START CHARGE
Adjust the AMPS according to how much PV I have (midday has loads, end-of-day when the PowerWalls become full will be 5AMPs - just enough to stop Exporting)

The above would be pretty ease to do in Software, I haven't found an existing solution, nor the time to create one (if anyone is interested speak up, it would be more worthwhile if there were any other takers)

One of my considerations is that the PowerWalls will charge at around 3kW on off peak (a rate that I read as "best for battery longevity"), but when PV is generating at full whack the PowerWalls don't max out until 10kW - a rate that is probably not good for them.

So I would prefer to charge the car at at least 16AMPs when PowerWall charging goes over, say, 7kW ... rather than "Fill PowerWalls flat out, then use Wall Charger CT to detect export and divert to car"

 

[Avendit]

This is where I am at too.

I installed a Zappi assuming I would just "allow any excess to charge the car".

In practice the right car (the one most empty / most needing miles "soon") needs to be attached to the Zappi (other charger is an old Tesla charger), that involves a driveway car-shuffle.

And then the business of overriding overnight schedule and remembering to re-engage it before a trip. Forgetting to enable means having to then stop and supercharge ... forgetting to disable overnight schedule means the car then charges overnight - costs me some money and then the car is full so no capacity to fill up with PV tomorrow ... all 1st world problems of course

I think it would be better if the car said that it wanted to charge, rather than the wall charger controlling that. Wall charger has no idea which car is plugged in / having the greater need for charging (going somewhere soon / lower SOC / Some other criteria)

I'm currently solving this by:

Plug both cars into wall chargers - both enabled to "charge" (rather than being in Eco+ Mode)
Leave the overnight Scheduled charge in place (for when I do want it)
Drop the LIMIT to 50% at the end of the solar-day (unless I want an overnight charge)
(I've set a TeslaFi Schedule @ 16:00 in case I forget; therefore I have to explicitly increase LIMIT on the few occasions when I actually want an overnight charge)
When PV generation is high then increase the LIMIT and START CHARGE
Adjust the AMPS according to how much PV I have (midday has loads, end-of-day when the PowerWalls become full will be 5AMPs - just enough to stop Exporting)

The above would be pretty ease to do in Software, I haven't found an existing solution, nor the time to create one (if anyone is interested speak up, it would be more worthwhile if there were any other takers)

One of my considerations is that the PowerWalls will charge at around 3kW on off peak (a rate that I read as "best for battery longevity"), but when PV is generating at full whack the PowerWalls don't max out until 10kW - a rate that is probably not good for them.

So I would prefer to charge the car at at least 16AMPs when PowerWall charging goes over, say, 7kW ... rather than "Fill PowerWalls flat out, then use Wall Charger CT to detect export and divert to car"

Cheers both. Annoyingly we are away with the car these couple of weeks when the panels have been pumping out masses of excess power. But, when back home I'm leaning towards a manual process too.

I think to stop the battery contributing, I need to set it to charge mode, at whatever %its at, then the Andersen solar mode will take care of charging. I think I'll leave the car set to over night charging, but manually initiate a charge when needed.

I need to run the faffing around a few times manually to work out the algo I want, and will then slowly pick bits to automate as best I can. So many different bits of tech involved I'm worried I'm going to need some kind of windows GUI automation solution with a virtual phone running some of the apps. Only the Tesla really has a proper API access .

 

[muhsec]

I've also recently pulled the trigger on solar, hopefully getting installed in 3 weeks time. I'm fortunate enough to have quite a large (almost) directly South-facing roof even so when I started getting quotes almost everyone was coming back suggesting 8-12 panels. It seems the installers are really trying to stick under the 3.68kw limit to avoid a DNO application. As others have suggested I want to max the system out so I persevered, had some installers just stop speaking to me, but now have 20 panels being installed for somewhere around 8kw total. I realise this is going to be above my inverter max output and it'll get "clipped" however for the rest of the time/year I'll be generating more overall so I think it's worth it. The panels after all are not particularly expensive.

Battery storage I think is entirely down to your household usage. I worked out that I needed somewhere around 14kwh of storage to maximise how much of our own solar we could use in the house, however with a couple of cars I can also dump excess power into I've gone for 10kwh of battery initially.

 

[94jdh]

I am thinking to pull the trigger on Solar installation. I will get some estimators coming later this week

my roof is east / west.
we both work from home most of the days (wife is always WFH) and she loves to run washing machine/dryer (sometimes both at the same time) during the day

what you guys think is the best capacity, including battery, to install??

10 panels east + 10 panels west + 8 kwh battery?

I'm also east and west but for two flat roof areas - for me it will give a better spread throughout the day, rather than a high midday peak.
As others have said, as many panels as you can afford, and if you use alot of electric in the evening and overnight then a good size battery(s) - you can also benefit from charging off a cheap tariff in the winter.

 

[Avendit]

. I realise this is going to be above my inverter max output and it'll get "clipped" however for the rest of the time/year I'll be generating more overall so I think it's worth it. The panels after all are not particularly expensive.

Agree completely - it's not the max you are buying for, it extending the useful generation as far into the shoulder seasons as possible you are buying for.

 

[btc1k]

I've also recently pulled the trigger on solar, hopefully getting installed in 3 weeks time. I'm fortunate enough to have quite a large (almost) directly South-facing roof even so when I started getting quotes almost everyone was coming back suggesting 8-12 panels. It seems the installers are really trying to stick under the 3.68kw limit to avoid a DNO application. As others have suggested I want to max the system out so I persevered, had some installers just stop speaking to me, but now have 20 panels being installed for somewhere around 8kw total. I realise this is going to be above my inverter max output and it'll get "clipped" however for the rest of the time/year I'll be generating more overall so I think it's worth it. The panels after all are not particularly expensive.

Battery storage I think is entirely down to your household usage. I worked out that I needed somewhere around 14kwh of storage to maximise how much of our own solar we could use in the house, however with a couple of cars I can also dump excess power into I've gone for 10kwh of battery initially.

The DNO's are an absolute pain in the a**e, it's no wonder installers want to stay under the 3.68 limit.

There is no joined up thinking - how the net zero will ever be achieved when there are so many restrictions in place by the DNO's - and if there is an upgrade required on the infrastructure somewhere - they want the individual customer to pay for it!

 

[muhsec]

There is no joined up thinking - how the net zero will ever be achieved when there are so many restrictions in place by the DNO's - and if there is an upgrade required on the infrastructure somewhere - they want the individual customer to pay for it!

The thing is if enough people on a street submit 3.68kw notifications, whether they end up installing it or not, the DNO can't refuse these by law and the cost of any infrastructure upgrade falls to the DNO. Just saying...

 

[phil4]

I'm still just sitting waiting. First enquired in Feb, DNO approved in May, two surveys carried out. But no date yet for install. And this is just the Solar part. I think they are suggesting (in a completely vague, "don't quote us" way) end of this year.

Really taking a long long time. And as I say, this is just Solar. PW they can't even order from Tesla as >15months delay... so I'm on a "Reserve" list for that. So expect that'll be 2024 perhaps.

So it's not just the DNO who are the pain, seems many solar installers are swamped.

 

[muhsec]

Cheers both. Annoyingly we are away with the car these couple of weeks when the panels have been pumping out masses of excess power. But, when back home I'm leaning towards a manual process too.

I think to stop the battery contributing, I need to set it to charge mode, at whatever %its at, then the Andersen solar mode will take care of charging. I think I'll leave the car set to over night charging, but manually initiate a charge when needed.

I need to run the faffing around a few times manually to work out the algo I want, and will then slowly pick bits to automate as best I can. So many different bits of tech involved I'm worried I'm going to need some kind of windows GUI automation solution with a virtual phone running some of the apps. Only the Tesla really has a proper API access .

I'm starting to play with this too. First step is installing a Shelly EM with CT clamps to start collecting usage data for the whole house, then I can write some code or IFTTT type functions to manipulate where any excess power will be diverted - looking to manage it between the house battery, immersion, and two cars.